Field
The described embodiments relate to techniques for communicating information among electronic devices, including techniques for enhancing the reliability of wireless communication among electronic devices in a multicast group.
Related Art
One wireless communication technique for providing content to multiple electronic devices uses of a multicast group. For example, the content may be sent to electronic devices that are members of the multicast group (which are sometimes referred to as “sink electronic devices”, “sink nodes”, or “sinks”) using a multicast transmission from an electronic device that is the source of multicast data (which is sometimes referred to as “source electronic device”, “source node”, or “source”). The source electronic device may be, for example, an access point (“AP”) or a source node in an arbitrary source-sinks scenario.
This communication technique allows resources (required for performing actions such as content generation, processing, and communication) to be shared. This sharing can reduce the overall power consumption, and the air time required for communication in comparison to multiple unicast communications. The multicast transmission can use a communication technique compatible with an Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard (which is sometimes referred to as ‘Wi-Fi®’).
However, there are multiple sources of inefficiency in current multicast mechanisms in wireless networks based on the IEEE 802.11 standard. In some legacy wireless communication networks based on the IEEE 802.11 standard, multicast transmissions sent by an AP and received at electronic devices in a multicast group do not benefit from any acknowledgement (“ACK”) mechanism. That is, in response to receiving multicast packets from an AP, the electronic devices in the multicast group do not send ACK packets to the AP to provide feedback on whether the packet sent was correctly received. The ACK is used by the AP as a measure of the quality of service of multicast transmissions perceived by the electronic devices. Additionally, the data rate allowed for multicast transmissions is only limited to a standard “basic rate set”, that is typically very low. For example, to send a physical layer convergence protocol data unit (PPDU) of 1500 KB size, only a 6 Mbps transmission rate is allowed (while other types of data can be transmitted at a 54 Mbps transmission rate), resulting in an air time of 2.02 milli-seconds (msec). Such a long required air time results in an inefficient airtime utilization that not only impacts the perceived Quality of Service (“QoS”) of the electronic devices in the multicast group, but also the overall performance of the wireless network in which the electronic devices participate.
In some other legacy wireless communication networks based on the IEEE 802.11 standard, an AP converts a multicast transmission into multiple unicast transmissions. This conversion allows individual ACKs to be sent back from each electronic device in the multicast group to the AP.
In other legacy wireless communication networks based on the IEEE 802.11 standard, a GroupCast with Retries (“GCR”) service is available. Based on GCR, the AP can retry multicast frames several times on its own discretion. The number of retries and the conditions based on which an AP attempts a multicast retry is typically implementation-specific.
In some other legacy wireless communication networks based on the 802.11 standard, GCR with block ACK (“BA”) is available. A block ACK is similar to a regular ACK, except that it reports correct reception of multiple MAC packets at a time. Based on this mechanism, an AP may establish a BA agreement with some electronic devices. Following this agreement, after a multicast transmission, a random subset of electronic devices in the multicast group—from a subset of electronic devices that have a BA agreement with the AP—may receive polls to provide BAs. Acknowledgments are not received from all electronic devices in the multicast group. However, the electronic device(s) being polled in the existing GCR service may not reflect the reception status of the other electronic devices in the multicast group. For example, some electronic devices may have very poor reception quality while the polled electronic devices may report successful receipt of multicast data. The polled electronic devices may have a significant impact on the overall multicast experience across all the electronic devices in the multicast group. However, the access point can have difficulty selecting the correct set of electronic devices that represent the overall/worst reception quality of the multicast group.
Moreover, this communication technique is unable to address the different requirements of the electronic devices in the multicast group, such as different latencies, different numbers of sinks and/or different amounts of interference from other APs (which is sometimes referred to as “Overlapping Basic Service Sets” or “OBSS”).